1. Field of the Invention
This invention generally relates to optical components generally and more particularly to parallel optical processing within a shared optical component.
2. Description of the Related Art
The telecommunications network serving the United States and the rest of the world is presently evolving from analog to digital transmission with ever increasing bandwidth requirements. Fiber optic cable has proved to be a valuable tool, replacing copper cable in nearly every application from large trunks to subscriber distribution plants. Fiber optic cable is capable of carrying much more information than copper with lower attenuation.
Currently this expansion of bandwidth is being accomplished by what is known as xe2x80x9cwavelength division multiplexingxe2x80x9d (WDM), in which separate subscriber/data sessions may be handled concurrently on a single optic fiber by means of modulation of each of those subscriber data streams on different portions of the light spectrum WDM is therefore the optical equivalent of frequency division multiplexing (FDM). Current implementations of WDM involve as many as 128 semiconductor lasers each lasing at a specific center frequency within the range of 1525-1575 nm. Each subscriber DataStream is optically modulated onto the output beam of a corresponding semiconductor laser. The modulated information from each of the semiconductor lasers is combined onto a single optic fiber for transmission. As this digital signal is passed across an optical network, it will be subject at various intervals to amplification by, for example, Erbium doped amplifiers and dispersion compensation by, for example, optical circulators with coupled Bragg filters. At each node in the network, e.g. central office or remote terminal, optical transceivers mounted on fiber line cards are provided. On the transmit side, a framer permits SONET framing, pointer generation and scrambling for transmission of data from a bank of lasers and associated drivers, with each laser radiating at a different wavelength. On the receive side, the incoming signals are separated into channels detected by photo detectors, framed and decoded.
Throughout the network a broad range of passive optical components are utilized to process optical beams from individual optical fibers.
Two port devices condition a single beam of light on a single optical path. An isolator blocks feedback to the source of an optical beam. A modulator uses an electro/magneto optic or other property of a crystal/wave guide to modulate a single beam of light passing through it. A filter blocks a portion of the spectrum of a single beam of light passing through it.
Three port devices handle more complex optical functions such as splitting/routing beams based on optical properties thereof. Three port devices, require precise alignment of two/three beams of light across two optical paths.
Circulators separate optical beams on the basis of the direction of their propagation. Thus a circulator can be used to separate the sender""s and receiver""s communications initially duplexed on a single optical fiber.
The multiplexers, demultiplexers, and interleavers are used to separate individual or discrete sets of channels of a WDM communication on a single optical fiber.
The power taps and splitters are used to split a single laser source into multiple optical beams at selected relative intensities.
The polarization beam splitters are used to separate arbitrarily polarized light into orthogonally polarized components. The combiners are used to perform the opposite operation.
The components are expensive to manufacture. In addition, one passive optical component is required for each optical fiber. A typical telecom installation at either the central office or relay site handles thousands of optical fibers each with their own associated passive and active components.
What is needed is a way to reduce the cost, complexity, and form factor(s) associated with providing active and passive optical components to optical fibers.
The present invention advantageously provides a method and apparatus for the parallel optical processing of a plurality of optical beams within a 2 port optical processing unit. The optical processing unit may perform any of the functions associated with 2 port devices such as: isolators, modulators, filters etc. The present invention further advantageously provides optimal and uniform coupling between each pair of optical fibers, i.e. each discrete pair of access ports, with the optical processing unit. This is achieved in part by a precise geometric arrangement of all elements of the apparatus. The present invention further advantageously provides a reduced form factor and cost when compared with individual 2 port devices.
In an embodiment of the invention an optical processor is disclosed for parallel optical processing of optical beams. The optical processor includes a first and a second lens system, an optical processor unit (OPU) and a first and a first and a second termination of optical fibers. The first lens system exhibits first focal points. The second lens system exhibits second focal points. The second lens system is spaced apart from the first lens system along a central axis in a substantially confocal configuration with respect to one another. The OPU is located between the first and the second lens system. The first and second termination of the optical fibers are displaced from one another along the central axis outside the first and the second lens systems. The first and second terminations include opposing ones of pairs of optical fibers with each pair providing two port access to said OPU. The first and second terminations are offset from the corresponding focal points of the first and second lens systems in a first direction along the central axis to reduce feedback of spurious reflection within the optical processor.
In an alternate embodiment of the invention an optical processor is disclosed with first and second lens systems spaced apart from one another in a non-confocal arrangement. The OPU is located between the first and second lens systems. The first and second terminations of the optical fibers are displaced from one another along the central axis outside said first and said second lens systems. Each of the first and second terminations are displaced from a corresponding one of the first lens system and the second lens system to locations for which the first and second lens systems effect a transverse magnification substantially equivalent to 1.
In another embodiment of the invention a method for parallel optical processing is disclosed. The method includes the acts of: effecting one of a convergence and a divergence of the optical beams from the first termination of optical fibers; optically processing the optical beams from the first termination; and effecting an other of the convergence and the divergence of the optical beams processed in said act of optically processing to form an image with a transverse magnification of substantially xe2x88x921 on the second termination of optical fibers.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.